1. Field of the Invention
The present invention relates to an ink jet printing apparatus and an ink jet printing method which successively stack a plurality of print mediums printed with an image one upon the other.
2. Description of the Related Art
An printing apparatus has an improved printing speed in recent years, with the printing time required to print on a print medium such as paper and a supply time and a discharge time between a print medium and the next (paper supply/discharge time) decreasing year by year. So a possibility is growing that, before a printed and discharged medium has its image dried enough, the next printed medium may be discharged and stacked on the first one. In that case, upon contact of the surface of the first printed medium and the back of the next printed medium, the printed image of the first medium may be disturbed and the back of the second medium smeared. Since ink on the printed surface of the first medium is not sufficiently dry, the back of the second medium may stick to the first because of the viscous ink.
Japanese Patent Laid-Open No. H06-091861 (1994) discloses a construction in which, when a next printed medium (also referred to as a “subsequent print medium”) is discharged onto a first printed medium (also referred to as a “preceding print medium”), the subsequent print medium is deflected. That is, by deflecting the subsequent print medium, the time at which the print medium comes into contact with the preceding print medium is delayed. Japanese Patent Laid-Open No. 2002-200741 describes a method of controlling the timing of printing on the subsequent print medium according to a parameter related to the ink drying time in the preceding print medium.
The print timing control method such as described in Japanese Patent Laid-Open No. 2002-200741 does not require a special construction of Japanese Patent Laid-Open No. H06-091861 (1994). However, the print timing control method assumes that print mediums of the same size are printed successively with images and discharged and stacked at the same position.
Therefore, when a plurality of print mediums of different sizes are successively printed with images, or when a plurality of print mediums of the same size, after being printed, are discharged and stacked shifted in a widthwise direction of the print medium, there is a possibility of the print timing being delayed more than necessary. That is, in the former case, because of the size difference between the preceding print medium and the subsequent print medium, there is a portion in these print mediums where they do not overlap when discharged. In the latter case, since the preceding print medium and the subsequent print medium are shifted in the widthwise direction when stacked one upon the other, these print mediums have a portion where they do not overlap. So, controlling print timing of the subsequent print medium without considering the portion where the preceding and subsequent print mediums do not overlap may result in the print timing being delayed more than necessary.